Java opts for the task tracker child processes. Subsumes ‘mapred.child.heap.size’ (If a mapred.child.heap.size value is found in a configuration, its maximum heap size will be used and a warning emitted that heap.size has been deprecated). Also, the following symbols, if present, will be interpolated: @taskid@ is replaced by current TaskID; and @port@ will be replaced by mapred.task.tracker.report.port + 1 (A second child will fail with a port-in-use if mapred.tasktracker.tasks.maximum is greater than one). Any other occurrences of ‘@’ will go unchanged. For example, to enable verbose gc logging to a file named for the taskid in /tmp and to set the heap maximum to be a gigabyte, pass a ‘value’ of:
-Xmx1024m -verbose:gc -Xloggc:/tmp/@taskid@.gc